"use strict";
let add = (a, b) => {
    return a + b;
};
let sub = (a, b) => {
    return a - b;
};
let chen;
chen = (a, b) => {
    return a * b;
};
let chu = (a, b) => {
    return a / b;
};
let pow = (a, b) => {
    return Math.pow(a, b);
};
//可选参数，在参数后面加？
function slice(str, start, end) {
}
slice('zehjiushiai', 5, 3);
slice('123', 1);
//形参默认值
function phone(str) {
}
